Integrated circuits (as well as other types of circuits) may include decoupling capacitors to provide a power buffer for the power supplies that provide power to the integrated circuits. These decoupling capacitors generally serve to compensate for an inability of power supplies to handle especially high-frequency changes in current requirements. Such changes may occur, for example, because the integrated circuit experiences high-frequency changes in power demands, due to, for example, a particular part of the integrated circuit rapidly varying between high and low utilization. In general, for some high-frequency power demand changes, associated power supplies are unable to properly follow such power demand changes. The decoupling capacitors thus provide a “buffer” of charge to compensate for this inability.
In general, circuit designers provide a number of decoupling capacitors of different values to serve this “buffering” function. Different anticipated frequencies of power demand changes call for different capacitor values. For example, one particular demand change frequency may be associated with a first particular capacitor value and another particular demand change frequency may be associated with a second particular capacitor value. In addition, different power supplies may have different associated demand change frequencies. To accommodate a wide range of demand change frequencies and power supply values, capacitors with various different capacitor values may be provided.
Part of designing circuitry is determining the number of the various capacitor values for the decoupling capacitors to be included. The process for determining these numbers, however, is generally tedious.